What does gravitational potential at a point mean?
Use your answer in (i) to explain why the gravitational potential near an isolated mass is always negative.
A spherical planet has mass $6.00 \times 10^{24}\,\text{kg}$ and radius $6.40 \times 10^{6}\,\text{m}$. The planet can be treated as isolated in space, with its mass concentrated at its centre. A satellite of mass $340\,\text{kg}$ is in a circular orbit around the planet at a height $9.00 \times 10^{5}\,\text{m}$ above its surface. For the satellite: show that its orbital speed is $7.4 \times 10^{3}\,\text{m s}^{-1}$.
Calculate the satellite’s gravitational potential energy.
Rockets on the satellite are fired for a short time. The satellite’s orbit is now closer to the surface of the planet. State and explain any change, if any, in the kinetic energy of the satellite.